The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a catheter and a balloon catheter used for diagnosis or treatment of a stenosis (also known as a stricture or obstruction) in a blood vessel or digestive organ.
A stenosis that is formed within a blood vessel, a bile duct, a pancreatic duct, or the like interrupts the flow of blood, bile (biliary fluid), pancreatic juice, or the like, respectively. A catheter is conventionally used for diagnosis or treatment of a stenosis.
A typical catheter comprises a tubular inner layer, an outer layer covering the outer circumference of the inner layer, and a reinforcing layer arranged between and bonding together the inner layer and the outer layer. In a catheter of this type comprising a reinforcing layer interposed between an inner layer and an outer layer, it is difficult to strengthen the bond between the inner layer and the outer layer.
Techniques have been developed to solve this problem. One of the techniques involves a catheter having a reinforcing layer with a wavy contour, an inner layer having an outer surface that follows the wavy contour of the reinforcing layer, and an outer layer having an inner surface that follows the wavy contour of the reinforcing layer (see Japanese Patent No. 4741151, for example). Another one of the techniques involves a catheter having a protruding portion that is disposed on an inner layer and that protrudes through a gap in a reinforcing layer toward an outer layer, and that extends in the distal direction to stick into the outer layer (see International Publication No. WO2015/012185, for example).
However, in the catheter described in Japanese Patent No. 4741151, the irregularities provided on the outer circumference of the inner layer and on the inner circumference of the outer layer merely have a wavy contour and no other irregularities are provided. In the catheter described in International Publication No. WO2015/012185, the protruding portion disposed on the inner layer extends in only one direction: from the proximal end toward the distal end. Therefore, there has been a problem that the outer layer readily comes off the inner layer when the outer layer is pulled in the distal direction due to the presence of a stenosis. This problem is more likely to occur when the catheter is inserted into a curved duct such as a blood vessel, a bile duct, or a pancreatic duct, in which case the catheter bends and stress is concentrated at the portion where the outer layer and the inner layer are bonded to each other.